Well ijust rebuilt a 350x that had an 89mm bore but now i have a 92mm JE piston in. The question is that I can't get it to run right. The engine is in a 250x frame.
Engine:
? cc
92mm JE piston
Shaved Flywheel
FST cam
Ti retainers and valve springs
38mm PE carb (need jet sizes Louisiana)
Uni pod Filter on carb
Ported and Flow tested head

The bike never idles spudders about 1/2 throttle. Has anyone used a 400ex carb or 38mm PE, If so can u tell me the jet sizes used?

 

I don't know if this will help out but a buddy of mine has a 250X with TC race cam, 12.5 to 1 piston, race ported and a 400ex carb with a 180 main jet bolt on air filter in Dallas, TX elevation. So I think you would need a little bigger than the 180 but I'm no expert on this so take it for what its worth.
CatCrap check your PM (Private Message) that should be blinking at the top of the posts when you log on if you haven't used it yet.
Later!